Modeling and Simulation of the Characteristics of Pneumatic Cushion Cylinders

The analysis of the characteristics of the cushion process of the pneumatic cushion cylinder is presented, and the nonlinear model of pneumatic cushion cylinders is built in the form of nonlinear differential equations. Besides, through the simulation of the pressure in the cushion chamber, the characteristics of the pneumatic cushion cylinder are obtained, which helps to understand the performance of the pneumatic cushion cylinder and improve or design the better cushion structure.

Path Classification and Estimation Model Based Prognosis of Pneumatic Cylinder Lifetime

Prognosis is a key technology to improve reliability,safety and maintainability of products,a lot of researchers have been devoted to this technology.But to improve the predict accuracy of remaining life of products has been difficult.To predict the lifetime specification of pneumatic cylinders with high reliability and long lifetime and small specimen,this paper put forward the prognosis algorithm based on the path classification and estimation（PACE） model.PACE model is based entirely on failure data instead of failure threshold.Pneumatic cylinders normally characterize with failure mechanism wear and tear.Since the minimum working pressure increases with the number of working cycles,the minimum working pressure is chosen as degradation signal.PACE model is fundamentally composed of two operations：path classification and remaining useful life（RUL） estimation.Path classification is to classify a current degradation path as belonging to one or more of previously collected exemplary degradation paths.RUL estimation is to use the resulting memberships to estimate the remaining useful life.In order for verification and validation of PACE prognostic method,six pneumatic cylinders are tested.The test data is analyzed by PACE prognostics.It is found that the PACE based prognosis method has higher prediction accuracy and smaller variance and PACE model is significantly outperform population based prognostics especially for small specimen condition.PACE model based method solved the problem of prediction accuracy for small specimen pneumatic cylinders＇ prognosis.

Simulation on the impact pneumatic cylinder with a reservoir

We proposed a novel impact pneumatic cylinder with a reservoir connected to the inlet chamber so that the pneumatic cylinder can achieve a high speed. A reservoir with high-pressure air enabled the cylirider to achieve considerable＇acceleration when it began to Work. We established a mathematical model to simulate the behaviors of an impact pneumatic cylinder, focusing on the relationships of the maximum piston speed with the air supply pressure and the reservoir volume. The results show that the reservoir .can help significantly enhance the pneumatic system velocity. When the reservoir volume is less than double the cylinder volume, an increase in the reservoir volume is more effective in increasing the maximum piston velocity.

Dynamic Friction Behaviors of Pneumatic Cylinders

This paper deals with experimental investigation and modeling of dynamic friction behaviors in the sliding regime of pneumatic cylinders. Using three pneumatic cylinders, friction characteristics are investigated and modeled under various conditions of velocity variation and pressures. It is shown that a hysteretic behavior can be seen at low velocities in the friction force-velocity relation and the friction force varies nearly linearly with the velocity at high velocities. The hysteretic loop is expanded to higher velocities when the frequency of the velocity variation is increased, and its size is increased with increasing driving pressure and is decreased with increasing resistance pressure. It is shown that such behaviors can be relatively accurately simulated by the new modified LuGre model in which a few static parameters are varied with the frequency of velocity variation.

A rotary pneumatic actuator for the actuation of the exoskeleton knee joint

Rotary pneumatic actuators that are made out of linear one are always best suited for exoskeleton joint actuation due to its inherent power to weight ratio. This work is a modified version of knee actuation system that has already been developed and major modifications are made in order to make it more suitable for human wearing and also to reduce its bulkiness and complexity. The considered actuator system is a rotary actuator where a pulley converts the linear motion of the standard pneumatic piston into the rotary motion. To prove the capability of the actuator, its performance characteristics such as torque and power produced are compared to the required torque and power at the knee joint of the exoskeleton in swing phase and are found to be excellent. The two-way analysis of variance（ANOVA）is performed to find the effect of the throat area valve on knee angle. The ANOVA shows the significant effect of the throat area variation on the knee angle flexion made by the proposed actuator. A relationship between the throat area of flow control valve, that is connected to the exit port of the direction control valve, and angular displacement of the knee joint has been formulated. This relationship can be used to design a control system to regulate the mass flow rate of air at the exit and hence the angular velocity of the knee joint can be controlled.

Pneumatic force servo system based on disturbance observer

In order to design a low-cost pneumatic force servo system with large output forces,a scheme of a booster cylinder controlled by high speed solenoid valves is proposed.A nonlinear model of the system is established,in which the hysteresis of high speed solenoid valve is considered.In order to deal with parameter uncertainty and disturbances of noise and friction,a feed-forward control method based on a disturbance observer is proposed.A practical pneumatic force servo system is used to testify the feasibility of the proposed controller.The experimental results show that pneumatic force servo system based on the proposed controller has high force tracking accuracy and quick response.

Application of Nonlinear Friction Compensation to Pneumatic Positioning

For a pneumatic actuator,precise positioning is difficult to obtain because of the compressibility of air and the static friction and Coulomb friction.This paper develops a nonlinear friction compensation scheme for precise positioning of a pneumatic system.This Scheme is tested by simulation and experiment and is shown to be effective.

Design and field evaluation of hill-drop pneumatic central cylinder direct-seeding machine for hybrid rice

To meet the requirement of the precision direct-seeding for hybrid rice,this study aimed to design a hill-drop pneumatic central cylinder direct-seeding machine to sow ten rows at a time.A series of orthogonal experiments were conducted to investigate the performance of the cylinder seeder.The influences of the hole diameters,degree of vacuum,and rotational speed of the cylinder were tested on JPS-12 computer-vision seeding test platform,and the rotational speed of 10-50 r/min,diameter of 135 mm and a negative pressure of 1.0-2.0 kPa were employed.Test results showed that the optimal parameter combination was a vacuum of 2.0 kPa and a hole diameter of 2.0 mm(straight hole),with a rotational speed of 30 r/min.The probability of(2±1)seeds in each hole was 95.3%,while the probability of seed-missing hole was 2.0%.A series of field experiments were then conducted to test the seeder performance according to China National Standard Test Methods,and the field test results showed that for the hill-drop pneumatic central cylinder direct-seeding machine,the probability of(2±1)seeds in each hill was 91.6%,while the probability of seed-missing hill was 2.7%.The yield data showed that the average effective panicle had 231.25 ears,the average seed setting rate was 9.92%,the average 1000-grain weight was 22.45 g,and the average yield was 7107.9 kg/hm^(2) that was 26.14%higher than the average yield of rice(5634.9 kg/hm^(2))of Guangdong Province in 2016.The results showed that the hill-drop pneumatic central cylinder direct-seeding machine for hybrid rice could be applied in practical precision rice seeding.

Dynamic Characteristics of a New Pneumatic Cylinder with Curved Groove

With the development of industrial automation technology, pneumatic systems are widely applied in many fields. The pneumatic cylinder is the most important actuator in the pneumatic system. This paper discusses the dynamic characteristics of a new pneumatic cylinder with a cushion ring and a special curved groove. This pneumatic cylinder can move at high speed and with low acceleration. The results of the experimental study and numerical simulation are presented. The simulation results agree well with the experimental data. Some new designs of the special curved groove are completed through numerical simulation. The experimental results show that the mean velocity of the improved cylinder is much greater than that of the original cylinder.

Design and experiment of the pneumatic cylinder type precision metering system for wheat

The main goal of this study was to design a pneumatic cylindrical-type metering device with six-rows for wheat precision and to analyze its output under different rotating speeds and vacuum pressure values.The effect of the pressure,rotating speed and rows on seed suction,retention and dropping was shown inspected.Six levels of rotating speed(5,10,15,20,25 and 30 r/min.)combined with the applying of different vacuum pressures(1.8,2.1,2.4,2.7,3.0,and 3.3 kPa)were inspected to detect the optimum pressure which was adequate for seed sucking at each speed.In addition,to predict the vacuum pressure corresponding with each rotating speed,a regression model was developed.Based on seed mass analysis,statistical differences under the influence of velocities and negative pressure were found at 5 percent significance according to Duncan’s Test,whereas the differences were existed between and within rows.Results revealed that the highest seed mass means of 19.02 g and 22.64 g were obtained by row1while the lowest means of 18.02 g and 21.49 g were attained by row6 under the effect of the speed and vacuum pressure,respectively.The noticeable variation between row1 and row 6,particularly under high speeds(25 and 30 r/min),might be returned to the truth that row 1 was closer to vacuum inlet,and row 6 was the farthest one.Results concluded that the multiple-row pneumatic cylinder with oblong shape seed nozzle was found to be capable for single seed picking with a small rows variation but without seed damage.

油气悬架阻尼数学模型对比分析

当前针对油气悬缸动力学特性的研究中,弹性力主要采用多变气体状态方程建模,阻尼力则采用薄壁小孔理论建模,由于真实情况中阻尼孔和单向阀的过流厚度都并非薄壁,而是具有一定的厚度,采用薄壁理论会导致模型在一定程度上失真,所以采用短孔过流理论建立阻尼模型,并考虑入口和出口的局部水头损失,重新构建油气悬缸动力学模型。通过施加真实道路采集的振动信号,对比了1/4悬架系统的两种阻尼力模型下的响应与真实的悬缸上支点加速度数据的平均绝对误差MAE和均方根误差RSME,验证了两个模型在低频范围都能较好模拟悬架振动,但中高频存在明显缺失,而短孔过流理论模型在频域上更逼近真实值。

气浮活塞优化设计及其径向承载力试验研究

对于气缸的高精度伺服控制而言,从根本上消除摩擦力具有重要的意义。气浮活塞是气浮无摩擦气缸的重要构成部件。在气缸的运行过程中,气浮活塞的径向承载力不足会引发活塞与缸筒内壁接触,致使气体润滑失效。为了提高无摩擦气缸中气浮活塞的径向承载性能,期望在实现更大承载力的前提下尽量减少耗气量,采用有限元仿真与试验相结合的方法,开展了气浮活塞径向承载力的研究工作。首先,采用Fluent软件仿真分析了供气压力、偏心率和节流孔直径等参数对气浮活塞径向承载力和耗气量的影响;然后,在综合考量后,优选出了气浮活塞的节流孔径,并以此加工出了气浮活塞样机;最后,为了测试实际情况下不同供气压力和偏心状态下的气浮活塞的径向承载能力,设计并搭建了一套以气浮无摩擦气缸作为加载装置的高精度径向承载力检测装置。研究结果表明:从定性的角度上看,仿真和试验结果趋势一致;从定量的角度上看,试验结果与仿真结果的吻合度在90%以上。该研究可为采用Fluent软件仿真研究气浮活塞径向承载力的准确性提供依据,为后续仿真模型的修正提供一定的指导。

比例阀控气缸系统确定性鲁棒反步运动跟踪控制器

为实现气缸运动轨迹的高精度鲁棒控制,建立了比例阀控缸系统的数学模型,并基于反步法设计了一种能够有效抑制系统模型参数不确定性、未建模动态和外界扰动等因素影响的非线性确定性鲁棒控制器。利用MATLAB中的Simulink模块构建气缸运动轨迹跟踪控制系统仿真模型。采用MATLAB/Simulink中的xPC-Target开发了基于非线性确定性鲁棒控制器的气缸运动轨迹实时控制系统。仿真结果表明所设计控制器是可行的。试验结果表明该控制器能够有效地跟踪参考轨迹,跟踪0.3 Hz正弦轨迹时的最大跟踪误差为0.89 mm,约为幅值的2.97%;跟踪0.4 Hz正弦轨迹时的最大跟踪误差为1.02 mm,为幅值的3.4%。

矿用卡轨车气动压绳梁的设计

为了解决无极绳牵引卡轨车在使用过程中压绳轮磨损导致的跳绳现象,本文基于部分矿区采用的人工拆除和安装压绳滑轮来防止跳绳的操作步骤,设计开发了一种气动压绳梁装置。该装置通过气动系统与压绳梁结构之间的装置联动,利用气缸的气动力实现压绳梁对于钢丝绳的压紧和放松,再由另外一个气缸完成销子的插拔,从而完成一个工作循环。该装置的使用,可以取代原本涉及人工的部分,提高生产工作的安全保障以及生产效率,在同类型的各个矿区中都可以进行推广使用。

一种高精度、长寿命超薄气缸的设计及制造

本文介绍了一种精度高、寿命长的超薄气缸,此超薄气缸由缸体、前端盖、活塞、后端盖及活塞杆等组成。该超薄气缸革新了气缸的装配生产工艺,完全避免了卡簧的使用,通过一体铆压成型可使气缸前后端盖完全密封,显著增加了气缸的密封性能,行程精度高,使用寿命提高至原来的3~5倍。该超薄气缸有望在机械、自动化及汽车等领域得到广泛应用,将为气动行业带来巨大的革新,经济效益显著,可为节能减排和带动当地经济发展做出较大贡献。

关于停放制动气路中缩堵的分析

停放制动在动车、机车、城轨和客车等车型中大量应用,停放制动气路中大多有节流缩堵,缩堵减缓了停放管路气体流动速度,尤其是当下游管路漏风时起到避免压力开关误报停放缓解信息及防止车辆带闸行驶的作用。该文使用Amesim软件对停放气路进行仿真建模,从仿真结果中分析选用合适孔径的缩堵,既可实现避免压力开关误报的功能,也可实现停放缸较快的充风和停放快速缓解。

气动夹具系统改进设计

某机加工企业因业务发展需要新接收一批零件,但该企业现有气动机床夹具设备不能胜任其定位及加工精度要求,在不增加过多成本的基础上,对现有气动夹具系统改进设计做详细论述,并给出各设计环节的气动系统图、设计说明及设计完成后的气动夹具总图。将设计完成后的夹具系统在Automation Studio 7.0 Professional软件中建模并仿真,分析各缸线性位置-时间关系;各缸起步伸出时在0~50 mm范围内3个缸同步,有效提高了设备的生产效率。在51~250 mm长度范围内夹紧缸运动速度开始降低,实现定位缸先定位。退出时由于夹紧缸垂直布置原因,在250~233.69 mm范围内出现微小波动,其波动范围在16.3 mm;由于此段为各缸退出段,对零件加工精度无影响。正常工作后各缸运行平稳,波动现象消失,满足加工要求。最后将改进后的气动系统和原系统作对比分析,结果表明:改进设计后的气动系统不仅能够完全胜任新零件的加工精度要求,且有效避免了原设备故障率高、维护保养困难、设备成本高、噪声大的诸多不足。

基于模型分析对动车组气动锁气缸偏心问题的探讨与改造

通过对动车组塞拉门辅助气动锁机构的观察,发现直线运动的力和旋转运动的力接触,将会使活塞杆在复位时受到水平分力影响,从而造成以下问题:活塞杆凹凸变形产生弯曲;密封圈左右摇晃密封不良;活塞总成前后端碰撞不均匀。据此开展试验结合仿真分析,最终验证了活塞杆运动时在原有的垂直力上还存在轴向力(即运动过程中活塞杆存在偏心现象)。基于此,提出活塞杆与转动杆的改造方案,将原有的2个部件合并为1个部件,减少运动时带来的轴向力,从而改变辅助气动锁工作模式,解决塞拉门关键技术问题,保障动车组运行安全。

汽缸摩擦力特性实验研究

研究汽缸的摩擦力特性.采用出口节流调速的方法建立汽缸摩擦力测试实验台,该实验台可进行汽缸的静动摩擦力测试.测试了汽缸在不同供气压力、不同速度和两腔压差下的动摩擦力特性,建立了汽缸的摩擦力模型,此模型将为研究汽缸的爬行现象和汽缸的伺服控制提供有意义的参考.实验结果表明:空载下汽缸的动摩擦力和速度的拟合关系为二次曲线;汽缸的动摩擦力与两腔压差及压差的方向都有关系.

气吸滚筒阵列式棉花精密排种器设计与试验

针对气吸式棉花精密排种器输气管路结构复杂、能耗大以及排种单体只能实现单行播种等问题,采用阵列吸孔吸种、侧向气吹清种等方式,设计了一种气吸滚筒阵列式棉花精密排种器,确定了该排种器关键零部件的结构参数,建立了充种过程的力学模型。以棉花种子为播种对象,以滚筒转速、吸孔直径、气室负压为影响因子,以合格指数、漏播指数和重播指数为排种性能指标,进行二次旋转正交组合试验,建立各影响因子与排种性能指标之间的回归模型,分析了各因子对排种性能的影响规律。采用多目标优化方法,确定最佳参数组合:滚筒转速为15.5 r/min,吸孔直径为3.5 mm,气室负压为4.2 k Pa,此时排种器的合格指数为93.5%、漏播指数为2.0%、重播指数为4.5%。经试验验证,试验结果与优化结果基本一致,满足棉花精密播种的要求。在此基础上进行了排种适应性试验,试验对象为几何特性存在一定差异的新陆早48号、新陆早52号、新陆早60号3种棉花种子,结果表明:合格指数均大于92%,漏播指数均小于3%,重播指数均小于5%,说明该排种器对不同品种的棉花种子具有一定的排种适应性。